The 1909 Winder U.S. Pat. No. 910,035 and the Misner U.S. Pat. No. 2,935,872 describe angle scale type wind speed indicators using what is effectively a wind drag pendulum or angle plate that provides a wind speed reading on an angle reading scale. A difficulty with the angle reading scale wind speed indicators is that they are difficult to read and do not afford convenient visual reading at a distance from the wind speed indicating device.
The Graham U.S. Pat. No. 2,040,305 differs from the angle scale type wind speed indicators in providing a linear reading scale. The wind drag pendulum, paddle or angle plate is rigidly coupled to a pivoting quadrant which in turn is connected to a vertical cable. The cable converts the rotary motion into linear motion. The cable is connected to a pointer which rides up and down in a slotted gauge to provide a linear scale reading.
The Post U.S. Pat. No. 1,344,315 similarly provides a wind speed reading by a pointer that slides up and down in a slotted gauge scale. In this patent, however, the pointer is coupled by a wire to a spring loaded wind drag plate that extends and retracts the wire in response to wind speed. Disadvantages of these linear scale wind speed indicators are the relative complexity of the mechanisms for converting the rotary motion of an angle plate anemometer to linear motion and the difficulty of reading wind speed from the pointer indicating linear scale at a distance from the devices.
The Hillman U.S. Pat. No. 3,871,220 is of interest because it describes a wind velocity and direction apparatus having a movable collar that can translate with limited motion on a mast in response to variable wind speed. The collar also rotates on the mast in response to changing wind direction. The collar is coupled to a fabric body wind sail "vane" that fills in response to the wind and is also able to rotate around the mast. The vertical displacement of the movable collar however is very limited and is solely for the purpose of moving an electrical coil relative to a ferrite core. This changes the reactance in an AC circuit and the variable AC signal from the AC circuit provides a direct measure of wind speed. The Hillman apparatus is therefore a limited motion transducer and in particular a "variable reactance" transducer wind speed indicator. The Hillman apparatus requires a complex mechanism and cannot provide direct visual reading of wind speed information at a distance from the device except through the use of the electrical signals.